1. Field of the Invention
The present invention relates to a rotary pilot valve suitable as means for operating a hydraulic working apparatus.
2. Description of the Related Art
In general, in a rotary valve, a directional control valve is mounted inside a valve main body, an output port, a tank port, and a pump port connected to the directional control valve are provided, and the directional control valve is controlled by operation of an operating lever, so that a pilot pressure supplied from the pump port can be supplied under control to the output port (see Patent document 1, for example).
As shown in FIG. 22, in a directional control valve with variable throttle in Patent document 1, a hole 61 is formed at an axial center in a valve housing 60 and a spool 63 is fitted in the hole such that the spool can rotate and slide in the axial direction freely. A pump port 67 is provided in a central portion of the valve housing 60, two output ports 65 and 66 are provided on opposite sides of the pump port 67, and two tank ports 68 are so provided on the other side of the valve housing 60 as to be positioned outside the output ports 65 and 66.
Operating shafts 70, 70 passing through sliding holes 69, 69 provided in lid bodies 64, 64 are connected to opposite ends of the spool 63 and one of the operating shafts 70 is engaged with an elongated hole formed in an operating lever 72 through a pin 71. A lower end portion of the operating lever 72 is engaged with a ball receiving groove 74 through a ball 73.
At a central portion of the spool 63, a notch-shaped liquid passage portion 75 having such a width as to connect the pump port 67 to the output port 65 or the output port 66 and having a depth gradually increasing from opposite side edges toward a central portion is formed.
If the operating lever 72 is operated by rotation in a rotating direction of the spool 63, i.e., if the operating lever 72 is turned in a direction perpendicular to a paper face of FIG. 22, an open area of the liquid passage portion 75 with respect to the pump port 67 can be reduced. After operating the operating lever 72 by rotation to make the open area of the liquid passage portion 75 a predetermined area, the operating lever 72 is operated by rotation in a transverse direction in FIG. 22 to slide the spool 63 in the axial direction. It is possible to allow a predetermined flow rate to flow from the output port 65 or the output port 66 which has been connected to the pump port 67 through the liquid passage portion 75 by sliding of the spool 63.
In the rotary valve described in Japanese Patent Application Laid-open No. 56-66570 (see line 10 in a lower right column on page 1 to line 5 in an upper left column on page 3 and FIGS. 1 to 7), the operating lever 72 need be operated in two steps in such a manner as to rotate the spool 63 and to slide the spool 63 in the axial direction in order to output pressure oil from the output ports 65, 66. Moreover, a pressing force in a diameter direction which acts on the spool 63 due to an oil pressure from the pump port 67 and sliding resistances between the lid bodies 64, 64 and the operating shafts 70, 70 when the operating lever 72 is operated are always applied to the spool 63.
Therefore, in order to operate the operating lever, an operating force resisting the pressing force in the diameter direction due to the pressure oil and the sliding resistances between the lid bodies and the operating shafts is required. As a result, the operating lever is heavy to be operated and physical fatigue builds up due to operation of the rotary valve, which worsens an operating environment. In addition, a structure including the lid bodies for allowing the operating shafts to project from the valve housing and a structure in which a sector-shaped plate 76 for supporting the operating lever is provided increase the number of parts as the rotary valve and the respective parts require high working accuracy, which requires much time to assemble the pilot valve.